Fit a bathroom wall cabinet to a lath and plaster wall

Fit a bathroom wall cabinet to a lath and plaster wall safely, finding real timber or masonry behind the laths for a secure fixing.

AB-01Gather your tools and check the cabinetLay out your tools and check the cabinet's fixing points on the back. Work out its loaded weight — cabinet plus bottles, mirror and shelves — because lath and plaster needs a stronger fixing than plasterboard for anything over a couple of kilos. Most cabinets need at least two, ideally four, fixing points.

1 each · Multi-detector (cable, pipe and stud)

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1 each · Spirit level, 600mm

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1 each · Tape measure

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1 each · Dust sheet

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AB-02Mark the fixing positionHold the cabinet against the wall at a comfortable height, usually with the mirror front around 1400-1500mm from the floor, and level it with a spirit level. Mark the fixing hole centres with a pencil. Stick a strip of masking tape over each mark first — it stops old lime plaster crumbling and skidding the drill bit off-mark.

1 each · Pencil

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1 roll · Masking tape

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AB-03Confirm what's really behind the plasterTap gently across the whole marked area. Genuine lath and plaster sounds dull and slightly springy — the plaster keys into timber laths, not a solid backing. A patch that sounds flatter and harder is often a later repair in dense modern plaster, or even plasterboard, which changes the fixing you'll need in later steps. Bathrooms are commonly patched or re-lined, so don't assume the whole wall matches.

AB-04Find the timber (or masonry) behind the lathsRun your detector over the marked area to pick up the line of nail or screw heads that fix the laths to the studs — these run vertically, usually every 400-600mm. Lath and plaster is almost always face-fixed to timber studs or battens, since it predates metal stud partitions, but confirm it: drill a 3mm test hole and check what comes out. Pale wood dust means timber; if you hit something solid and stop dead around 25-40mm in, that's masonry behind the battens; fine grey swarf means you've found a rare metal batten or a later metal-framed repair.

1 each · HSS drill bit, 3mm

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AB-05Check for cables and pipes, then check your stopcockCables and pipes can run almost anywhere in a bathroom wall, including up to taps, showers and shaver points. Sweep the area with your detector, then still treat it as if something's there until you've proved otherwise — detectors miss cables that are deep, in metal conduit, or outside the usual safe zones. Find your stopcock now, usually under the kitchen sink, and check it turns freely so you can shut the water off fast if you hit a pipe. If you have any doubt about what's behind the wall, isolate the relevant circuit at the consumer unit before drilling.

AB-06Drill the pilot holesFor timber behind the laths, drill a 3mm pilot hole into the centre of the stud, through the plaster and lath, to a depth matching your screw. For masonry behind battens, drill through the plaster and lath first, then switch to a 6mm masonry bit for the brick or block, going in 40mm past the batten. If you found plasterboard on metal studs instead, stop and switch to the metal-stud fixing in the next step — do not force a wood screw through steel.

1 each · Masonry drill bit, 6mm

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AB-07Choose the right fixing for your wallTimber stud behind the laths: a 60-75mm wood screw straight into the stud centre, no plug needed. Masonry behind battens: a 6mm wall plug with a 50mm masonry screw, giving 40mm of grip in the brick. If you actually found dot-and-dab plasterboard, use a fixing long enough — usually 75-100mm — to pass through the adhesive dabs and into the solid masonry behind, with a plug. If you found metal studs, use a self-drilling metal-stud fixing or spring toggle rated for the weight — never a plain plastic plug and never an ordinary wood screw, both strip straight through 0.5mm steel.

1 pack · Wood screws, 60mm (pack of 8)

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1 pack · Wall plugs, 6mm (pack of 10)

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1 pack · Masonry screws, 50mm (pack of 8)

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1 pack · Self-drilling metal-stud fixings (pack of 4)

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AB-08Fit a batten if your fixing points miss the timberLath and plaster on its own is too crumbly to trust with a heavy cabinet if your fixing point falls between studs. Screw an 18x44mm timber batten horizontally across at least two studs at cabinet height, using 60mm screws into each stud, then fix the cabinet to the batten instead of straight into the plaster. This spreads the load and stops the old plaster cracking around the screws.

1 each · Timber batten, 18x44mm x 1m

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1 pack · Wood screws, 60mm (pack of 8)

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AB-09Mount the cabinetLift the cabinet onto its fixings, or hold it in place and drive the screws through the back panel if it doesn't have keyhole hooks. Get someone to help hold it steady if it's heavy or awkward. Check it's level before you tighten fully, then tighten evenly — don't overtighten into lath and plaster, as it can crack the plaster around the screw.

AB-10Check it's secure and levelGive the cabinet a firm, steady pull to check nothing moves. Load the shelves with the heaviest items you expect to store, and open and close the door a few times to check it doesn't catch or pull the cabinet forward. Re-tighten any fixing that shows the slightest give before you finish.

AB-11Seal the top edge near splashesIf the cabinet sits close to a basin or shower, run a thin bead of sanitary silicone along the top edge where it meets the tiles. This stops water tracking behind the cabinet and soaking into the old plaster, which can loosen the laths over time. Smooth it with a wet finger and wipe off the excess straight away.

1 tube · Sanitary silicone sealant

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AB-12If your cabinet has a built-in light or shaver socketWiring a light or shaver socket into a bathroom is electrical work in a special location under Part P of the Building Regulations. Don't wire it in yourself unless you're competent to certify it — get a qualified electrician to connect and test it. This applies even if the cabinet itself is simple to hang.

RULES

KNOW THE RULES

Electrical work in bathrooms falls under Part P of the Building Regulations because of the water risk. Connecting a light or shaver socket should be done or checked by someone competent to certify the work.

AB-13Clean upVacuum plaster dust and drill debris from the floor, windowsill and bath before it gets trodden in. Wipe down the tiles and cabinet with a damp cloth, and put your tools away.

1 each · Cloth

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